1. Field of the Invention
The present invention relates to an image sensing device and to a method of fabricating the same, and more particularly, to an image sensing device having reduced pixel-to-pixel crosstalk and quantum efficiency, and a method of fabricating the same.
2. Description of the Related Art
An image sensor converts optical information into electrical signals. Recently, with advanced development of the computer and communications industries, there has also been an increasing demand for more highly-efficient image sensors for various fields such as digital cameras, camcorders, personal communication systems, game devices, surveillance cameras, micro-cameras for medical use, robots, and so on.
A unit pixel in an image sensor converts incident light into an electrical signal, and integrates charges corresponding to the amount of light at a photoelectric converter. In addition, a unit pixel of an image sensor reproduces an image signal through a readout operation. However, the incident light may form charges that are not integrated at the photoelectric converter of the unit pixel. For example, in a CMOS image sensor, charges may be moved to and integrated at a photoelectric converter of an adjacent pixel, causing what is known as pixel-to-pixel crosstalk.
Referring to FIG. 1, pixel-to-pixel crosstalk may be divided into the following categories: (a) optical crosstalk A, which occurs when a reflected light 6 is transmitted to a photoelectric converter 2 of a unit pixel adjacent to a relevant unit pixel, a reflected light 6 is formed by reflection from a top or side of metal wirings M1, M2, and M3, or a refractive light is formed by refraction at a non-uniform layer or at a multilayered structure including interlayer insulating layers having different refractive indexes; and (b) electrical crosstalk B, which occurs when charges generated at a lower or side portion of a photoelectric converter 2 of a relevant unit pixel are delivered to the photoelectric converter 2 of an adjacent unit pixel via a long-wavelength incident light 7.
For a black and white image sensor, when crosstalk occurs, resolution decreases causing image distortion. Meanwhile, for a color image sensor using an RGB color filter array (CFA), the probability for crosstalk to occur due to red light having a long wavelength is high, which may cause poor tint quality. Moreover, crosstalk may cause blooming effect in which adjacent pixels for an image are blurred.